My 1997 F-150 4.2 shows codes P1537 & 1538. IMRC valve stuck open. How to change on 1997 Ford F-150

Where is this and how hard is it to change?

Asked by for the 1997 Ford F-150
its a vac diapharm located behind the eng blk against firewall. the problem can be vac related or vac resivoir or rod clips,diapharms themselves or siganl